Receiver arrangement



Dec. 24, 1929. 5, LOEWE 1,740,864

RECEIVER ARRANGEMENT Filed April 27, 1927 wt-Q9 INVENTOR SIEGMUND LOEWE 0 45 M 0144 TORNEY Patented Dec. 24, 1929 UNITED STATES PATEllT OFFlCE SIEGMUND LOEWE, OF BERLIN, FRIEDENAU, GER-MANY, ASSIGIIOR TO RADIO COE- IPORATION OF AMERICA, A CORPORATION GE DELAWARE RECEIVER ARRANGEMENT Application filed April 27, 1927, Serial No. 186,880, and in Germany December 18, 1923.

The subject matter of this application is disclosed in my application filed in Germany December 18, 1923.

It is well known that by regeneration a considerable reinforcement of receiver actions is attainable. An unfortunate fact is that the action becomes noticeable only if the regeneration is pushed to a point so that self-oscillation is very close. Now, this latter phenomenon, on the one hand, impairs the quality of reception, that is to say, clearness of speech and musical reproduction, while, on the other hand, by re-radiation of the incoming oscillations by way of the receiving' antenna into space, it causes trouble to the whole neighborhood.

It is an object of this invention, therefore, to devise a receiver including one or more regeneration circuits which automatically become stabilized in the manner that, should the critical coupling be exceeded where normally self-oscillation would start, no oscillations will as a matter of fact be produced.

This aim is realizable, according to the disclosures of the present invention, by that means are provided which counteract the tendency of self-oscillations being produced, such means, however, becoming actually operative only when oscillations are really arising. This practically amounts to a limitation of the ensuing oscillations to an infinitely, or almost infinitely small, amplitude.

The first point to be taken into consideration in this connection is as follows: The means tending to dampen the oscillation must not be operative, whenever audible frequencies are concerned that tend to arise. Indeed. they should only be active whenever radio frequency oscillations in statu nascendi, as it were, are concerned. By the use offair-core couplings (contradistinct to what is true of ironcored couplings), it is possible to bring about the efiectiveness of the oscillation-damping means only in the desired case and circumstances.

For the same purpose, also condensers of different .size may be used which, as is well known, according to size, are adapted to allow of the operation or flow of different frequencies or of suppressing thesame.

One embodiment showing a solution of the problem as based upon the basic idea of this invention is shown by way of example in the accompanying drawing.

1 is an antenna whence the oscillations are fed to a tuned circuit 2 and further to tube 3 arranged audioirfashion. The plate cir cuit contains in well known manner the plate battery 5 shunted by condenser 4 and the telephone 6 as well as the back-coupler coil 7, which, in the presence of unduly close couplin causes the whole system to oscillate. However, between grid and filament, preferably with the insertion of a potentiometer 8, there is connected a rectifier 9 (for instance, a detector or hot-cathode tube) in series with a coil 10 which is in coupling relationship with another coil 11 inserted in the plate circuit. If the coupling between coils 10 and 11 is imagined to be absent, for the time being, the grid leak by way of the detector to the potentiometer substantially represents an arrangement which, on the one hand, imparts a certain biasing potential to the grid, while, on the other hand, it possesses diifen ent conductivity in the two directions of flow of the current. 'Now, this latter property, i. e., different conductance in both directions, is not utilized pro tem. The whole system 9, 10, 8, in well known manner serves as a grid leak. Now, if the back-coupling; by way of coil 7 is made too close, oscillations will be produced which through couplings 10 and 11, with the interposition of detector 9, are transferred to the grid in such a way that the grid is given a biasing potential unsuited for wave generation. Hence, the characteristic of the tube, as it were, is shifted as a consequence, i. e., by action of the change in biasing potential, to a less steep part of the curve so that no oscillations are liable to arise.

Such stabilization is accomplishable particularly easily, if the coils 7 and 11 are simultaneously coupled more closely and more loosely. No reaction whatever upon the audio-frequency part of the system need to be feared since the air-core coupler coils 10 and 11 do not appreciably transfer the lowfrequency oscillations.

Also other methods adapted to shift automatically the working point of the tube characteristic into the flat portion thereof at the time oscillations arise, are applicable with equal success to the present purpose.

Of course, circuits specially coupled with the plate circuit or some other part of the high frequency system could be provided adapted to choke oif radio frequency oscillations at the Very instant they arise.

What is also suited for the present purpose, by the way, is a potential source whose potential decreases as the current absorption grows. The flowing of a certain grid current is in evitably associated with the production of oscillations. Hence, if in the grid circuit a potential source is connected with a very high internal resistance (for instance, a Zamboni column (pile) or a battery with a very high resistance in series) also the mean grid potential will vary automatically with the flow of current in the grid circuit. Also in this way an automatic shift of the characteristic or detector between the grid and filament of the tube, and means in series with the detector and coupled to said feed-back arrangement for biasing the tube in a manner such that sustained radio frequency oscillations of high amplitude cannot exist.

2. A radio receiving circuit comprising a vacuum tube, a regenerative feed back circuit, a second feed back circuit for biasing the tubergrid at a bias unadapted for the production of sustained radio frequency oscillations, comprising. an air cored inductance and a detector in series. said series connection being between the grid and filament of said tube, and a second air cored inductance in the regenerative circuit of the tube coupled to said first mentioned inductance.

3 In a receiving system, a vacuum tube having a regenerative coupling between its input and output circuits, and means providing an additional coupling between the input and output circuits, said means including a detector between the grid and filament of said tube. a

4. In a recelving system, a vacuum tube having a regenerative coupling between 1ts input and output circuits, and meansproput and output circuits, and a grid leak path between the grid and filament of the tube, said path including a detector and an impedance, said impedance being coupled with the output circuit.

6. In a receiving system, a vacuum tube having a regenerative coupling between its input and output circuits, and means providing a grid leak path between the grid and filament coupled to said regenerative coupling to prevent sustained radio frequency oscillations.

7. In a radio receiving circuit, a vacuum tube having a feed-back circuit between its input and output circuits, and means between grid and filament of said tube to prevent sustained radio frequency oscillations, said means including a detector and impedance, said feed-back circuit including means to couple it to said impedance.

8. In a receiving system, a vacuum tube having regenerative coupling between its input and output circuits, a detector and reactance in series between the grid and filament of said tube, and a second reactance connected to said coupling and coupled to said first reactance.

9. A method of stabilizing a regeneratively coupled vacuum tube receiving circuit which consists in providing a path from the grid and filament of the tube for radio frequency input current, and subjecting current flowing through said path to a portion of the regenerative circuit whereby sustained radio frequency oscillations are effectively prevented. V

10. A method of stabilizing a regeneratively coupled vacuum receiving circuit, which consists in providing a path from the grid to the filament of the tube for a portion of the ratio frequency input current, and coupling said path to a port-ion of the regenerative circuit, whereby oscillations in said regenerative circuit bias said grid to a potential unsuitable for wave generation.

SIEGMUND LOEWE. 

